The Multi-Color Graphics Array or MCGA is a video subsystem built into the motherboard of the IBM PS/2 Model 30, introduced in April 1987, and Model 25, introduced later in August 1987; no standalone MCGA cards were ever made.
The PS/2 chipset's limited abilities prevent EGA compatibility and high-resolution multi-color VGA display modes.
256-color VGA games ran fine on MCGA as long as they stuck to the basic 320 × 200 256-color mode and didn't attempt to use VGA-specific features such as multiple screen pages.
Some games, including point-and-click adventures from Sierra On-line and Lucasfilm Games, as well as simulation and strategy titles from Microprose, solved this problem for low-resolution titles by supporting the MCGA's 320 × 200 256-color mode and picking the colors most resembling the EGA 16-color RGB palette, while leaving the other available colors in that mode unused.
An alternative approach used by a small number of (generally earlier) games was to use four-color CGA assets but make use of the adaptor's ability to freely change the palette for a slightly enhanced appearance.